Manufacture of persulfates.



"siding at Munich,

TEN FTEL GUSTAV ADOLPH AND ALBERT,PIETZSCH, OF MUNICH, GERMANY.

MANUFACTURE OF PERSULFATES.

No Drawing.

'same is based on the utilization of persulfate of ammonium, such'as canbe readily obtained by electrolytic methods, for this purpose. In thisart, the production of potassium-persulfate is at present carried outeither by directly preparing the same electrolytically, or by the.conversion of ammonium-persulfate. The latter method has the advantagethat. it takes as a starting product ammonium-persulfate which isreadily obtainable by electrolytic methods,

while the potassium-persulfate" can only be obtained with difficultyand-with very poor yields. of starting with ammonium-persulfate,however, resides in the fact that the ammoniumpersulfate isflreacted onby potassium-carbonate, a very costly reagent, and that thereafter theammonium-sulfate mustbe regener ated from the ammonium carbonate by theaid of sulfuric-acid.

V The object of the present invention is to overcome the difficultyabove pointed out, and

with this object in view, the applicants have devised the presentinvention which is based on the discovery made by them, thatpotassium-persulfate may be direct-1y obtained from the sulfatesof.potassium, under which term are to be understood not only the neu-'tral sulfatesbut other sulfates, such as bisulfateof potassium, saidreaction proceeding according tothe equatlons z thisimanner the ammoniumpersulfate Specification ofLetters Patent.

A disadvantage of the said method Leda-( essa Patented Apr. 22, 1913.

Application filed October 6, 1910. Serial N 0. 585,571.

may be readily and simply converted into persulfate of potassium, asulfate-of-ammonium solution being obtained as one of the byproducts ofthe reaction, from which an ammonium-persulfate solution may be readilyobtained electrolyticallydirectly or with the addition of sulfuric-acid.From this it will be seen that the manufacturer has it in his power toregenerate the ammonium-persulfate continuously during the process andas the same is required.

Under the present invention potassium persulfate is directly obtainedfrom potassium sulfate with as advantageous a utilization of theelectric current as in the case Where ammonium persulfate is obtainedfromammonium sulfate. This new process is based on the fact that, asapplicants have found, solutions of ammonium persulfate which has beenobtained by known electrolytic methods, may be directly acted on bysulfate of potassium in solid formiand undissolved, in such a way thatan ammonium sulfate remains in the solution.

The following example is given for the purpose of fully disclosing theinvention:

Example 1: To an ammonium-persulfate,

solution obtained. electrolytically, there is added an equivalent amountof'potassiumsulfate or of potassium-bisulfate in a powdered or solidform, the mixture being vigorously agitated and gently heated. Thepotassium-persulfate isimmediately separated from the solution intheform of fine crystalline laminae orplates, and may be separated bythe usual methods, such as siphon- .ing ofi' liquid, by decanting,

tion, or otherwise. The remaining solution of ammonium-sulfate, eitherin the neutralform or as bisulfate, can then be regenerated toammonium-persulfate by sub jecting the same to electrolysis.

- The applicants have further found that the conversion ofammonium-persulfate to potassium-persulfate can be carried out toparticular advantage when this is done in connection With theelectrolytic action in the electrolyzer, for which purpose ,a mixture ofammonium sulfate and potassium sulfate, under which terms are to beunderstood either .the neutral or bisulfates, is directly centrifugalacutilized. Under these conditions, the ammonium-persulfate is formed atthe anode with the usual. good yields, amounting to 80% and upward. Thisfreshly generated ammonium-persulfate is, however, immediately and atthe moment of its format-ion converted into potassium-persulfate andammonium-sulfate by the reaction of the potassium-sulfate existing inthe bath or solution. The potassium-persulfate thus formed is thrown outin solid form. and the ammonium-sulfate is then. again converted intothe persulfate, under the action of the current. Under this method ofproceeding, it is, therefore, only necessary to supply thepotassium-salt as fast as it is consumed, by additions of furtherquantities of potassiumsulfate (neutral or bis'ulfate) in order toobtain a continuous uninterrupted production of potassium-persulfatewith high yields. very great advantage in this connection is,

that the process may be carried out without the intervention of adiaphragm, for the reason that practically no persulfate remains insolution. The following example will serve to more fully disclose thismodification of the process.

' Example 2: A solution of 200 grams of ammonium-bisulfate together,with 400 grams of potassiunrbisulfate is subjected to electrolysis inthe usual manner with the aid of platinum electrodes and without theintervention of a diaphragm, the electrolyte remaining constantly incontact with solid potassium-bi'sulfate. Under this treatment solidpotassium-persulfate is thrown down in the bath whileammonium-bisul-fate goes into solution. This process may be carried .outwith a yield of from at the anode, while the reduction does 'notexceedmore than 1. to 2%. A surprising discovery made by these applicants inthis connection is, that by the same treatment sodium-persulfate, a bodywhich has been'very difficult to obtain heretofore, being very readilysoluble, can be obtained with ease. Hitherto this'salt could not even beobtained with the aid of carbonate of sodium fro-m am monium-persulfate;it was necessary for this purpose to employ caustic sodaor sodium--hydrate, the escaping ammonia under this treatment having been absorbedwith sulfuric-acid. The applicants havefound that by using the same-method as above de-' scribed, the ammonium-persulfate may be readilyconverted into sodium persulfate, leaving asa by-productammonium-sulfate,

by treating the said ammonium-,persulfate with sodium-sulfate (neutralor bisulfate). Here again, the conversion may be carried outconcurrently with the electrolysis with particular advantage. However,in this case, -in viewl of the ready solubility of sodium-persulfate,the two electrodes must be separated by a diaphragm. After theelectrolyte has been saturated with sodiumpersulfate, the latter beginsto be precipi tated, the sodium-salt thus precipitated being replacedbysodium-bisulfate. In order to more fully disclose this process thefollowing example may .serve p Example 3: A solution of 500gramssodium-bisulfate together with 500 grams amperiod of time,sodium-persulfate begins tov The be precipitated-in the anode space.

-yield under this process attains about 80%.

It will be noted that the term sulfates as employed in the claimsincludes not only the neutral sulfates but also the bisulfates.

What we claim and desire to secure by Letters Patent is as follows:

1. The. process of obtaining a persulfate of an alkali-metal, whichconsists in causing a sulfate of said alkali-metal in an undissolvedstate to react on a bath of ammonium persulfate.

y 2. The process of obtaining a persulfate of an alkali-metal, whichconsists in mixing ammonium sulfate in abath with a sulfate of analkali-metal and subjectingthe bath to electrolysis.

3. The process of obtaining a persulfate of an alkali-metal, whichconsists in sub- 'jecting a bath containing ammonium sulfate and a.sulfate of-said alkali-metal to electrolysis, and adding fresh suppliesof alkalimetal sulfate as the conversion of the alkalimetal sulfate intothe persulfate proceeds, to reconvert persulfate of ammonium into thesulfate.

4. The process of obtaining a 'persulfate of an alkali-metal, whichconsists in subjecting' 'a bath containing ammonium. sulfate and,undissolved. alkali-metal sulfate to' electrolysis, and adding freshsupplies of solid alkali-metal sulfate as the electrolysis proceeds, toreconvert persulfate of' ammonium into the sulfate. Q i

5. The process of obtaining potassium:

persulfate, which consists in causing a sulfate of. potassium in anundissolved state to react on a' solutlon of ammoniumrpersulfate.

'6. The process of obtaining potassiumpersulfate. which consists insubjecting a bath containing a potassium-sulfate and ammonium-sulfate toelectrolytic action.

7. The process of obtaining persulfate, which consists in su jecting aotassiumbat-h containing potassium-sulfate and amour signature s in thepresence of two witmonium sulfate to electrolytic action, and nesses.

adding fresh supplies of potassium sulfate GUSTAV ADOLPH. to the bath asthe reaction proceeds to re- ALBERT PIETZSCH.

5 convert persulfa-te of ammonium to the Witnesses:

sulfate.

A. VERE W. fCo'rTER, In testimony whereof we hereunto aflix MATHILDE K.HELD.

